The present invention relates to a slide guide structure incorporating a cam groove and a cam follower, and more particularly to a lens barrel apparatus having the foregoing structure.
In recent years, zoom lenses of a type arranged to change the distance between lenses to continuously change the focal distance have widely been employed. A lens moving apparatus has been disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 4-125605. The apparatus incorporates a spring member causing a cam surface and a cam follower surface to be brought into contact with each other so that "looseness" is prevented.
A molded plastic element and a slide guide structure disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-177130 constitute a dual structure consisting of first and second molded elements constituted by the molded plastic element and formed into cylindrical shape. Moreover, a spiral cam groove is formed in the inner surface of the structure. Thus, looseness can be prevented when the cam follower slides along the cam groove.
The lens moving apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 4-125605 must have the additional spring. Also the assembling process must have a step for assembling the spring. Therefore, the productivity deteriorates.
The slide guide structure disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-177130 is able to moderate the looseness owing to the elasticity of the molded plastic element. The dual structure causes the number of molded elements and assembling steps to be increased.
Moreover, a specific method of moving the lens has not been described in both of the conventional techniques. In addition, no description has been made about the operation permitted by the disclosed structure.
When the performance of a photographing lens is improved, a complicated structure is required because the number of the elements is increased. Thus, the size of the structure cannot be reduced. When the lens is slid, the degree of deflection varies in the sliding stroke. Therefore, a uniform state of contact cannot completely be maintained, causing "looseness" to occur. Hence it follows that smooth movement is inhibited. Moreover, the state of contact cannot be maintained at the stop position due to external force or excessive vibrations. As a result, stable holding of the lens is sometimes inhibited.
In view of the foregoing, an object of the present invention is to realize a mechanism for a lens barrel apparatus having a simple structure, incorporating a small number of elements and permitted to be operated without any looseness by a structure having a cam and a cam follower.